Electroactive fluorene copolymers and devices made with such polymers

ABSTRACT

The present invention is generally directed to copolymers of fluorene. It further relates to devices that are made with the copolymers.

This application is a Divisional of U.S. application Ser. No.10/137,898, filed May 2, 2002, now U.S. Pat. No. 7,074,885, which claimsthe benefit of 60/288,314, filed May 3, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electroactive fluorene copolymers. Theinvention further relates to electronic devices in which the activelayer includes such polymeric materials.

2. Description of the Related Art

Organic electronic devices such as devices that emit light, such aslight-emitting diodes that make up displays, are present in manydifferent kinds of electronic equipment. In all such devices, aphotoactive layer is sandwiched between two electrical contact layers.At least one of the electrical contact layers is light-transmitting sothat light can pass through the electrical contact layer. Thephotoactive layer emits light through the light-transmitting electricalcontact layer upon application of electricity across the electricalcontact layers.

It is well known to use organic electroluminescent compounds as theactive component in light-emitting diodes. Simple organic molecules suchas anthracene, thiadiazole derivatives, and coumarin derivatives areknown to show electroluminescence. Several classes of luminescentpolymers have also been disclosed. These include, for example,poly(1,4-phenylene vinylene) and derivatives; polythiophenes,especially, poly(3-alkylthiophenes); and poly(p-phenylenes). Alkyl anddialkyl derivatives of polyfluorene have also been disclosed, as in U.S.Pat. Nos. 5,708,130 and 5,900,327.

There is a continuing need for photoactive compounds having improvedefficiency and processes for preparing them.

SUMMARY OF THE INVENTION

The present invention is directed to copolymers comprising at least onefirst monomeric unit and at least one second monomeric unit, wherein theat least one first monomeric unit has a Formula I shown in FIG. 1, andthe at least one second monomeric unit is selected from (i) aromaticgroups having Formula II shown in FIG. 2, (ii) 6-membered-ringheteroaromatic groups having Formula III, shown in FIG. 6; (iii)5-membered-ring heteroaromatic groups having Formula IV, shown in FIG.7; (iv) aromatic groups having Formula V, shown in FIG. 8, (v) fusedring aromatic groups having Formula VI, shown in FIG. 9, Formula VII,shown in FIG. 10, and Formula VIII through Formula XI, shown in FIG. 11,and (vi) combinations thereof, where:

-   -   in each of Formulae I, II, III, IV, V, VI, VII, VIII through XI:        -   R is a substituent on a carbon atom which can be the same or            different at each occurrence and is selected from hydrogen,            alkyl, aryl, heteroalkyl, heteroaryl, F, —CN, —OR¹, —CO₂R¹,            C_(ψ)H_(θ)F_(λ), —OC_(ψ)H_(θ)F_(λ), —SR¹, —N(R¹)₂, —P(R¹)₂,            —SOR¹, —SO₂R¹, —NO₂, and beta-dicarbonyls having Formula XII            shown in FIG. 12 and as further described below under            “Formula XII”; or adjacent R groups together can form a 5-            or 6-membered cycloalkyl, aryl, or heteroaryl ring,        -   such that:        -   R¹ is a substituent on a heteroatom which can be the same or            different at each occurrence and is selected from alkyl,            aryl, heteroalkyl and heteroaryl; and        -   ψ is an integer between 1 and 20, and θ and λ are integers            satisfying Equation A1 below:            θ+λ=2_(ψ)+1;  (Equation A1);    -   in each of Formulae II, III, IV, V, VI, VII, VIII, and IX:    -   E can be the same or different at each occurrence and is a        single bond or a linking group selected from arylene and        heteroarylene;    -   in Formula IV:    -   A is independently at each occurrence C or N and γ is 0 or an        integer selected from 1 or 2, such that when both A are N, then        γ is 0; or when one of A is N and one of A is C, then γ is 1; or        when both A are C, then γ is 2;    -   Q is O, S, SO₂, or NR¹ where:        -   R¹ is a substituent on a heteroatom which can be the same or            different at each occurrence and is selected from alkyl,            aryl, heteroalkyl and heteroaryl;    -   in Formula V:    -   Q¹ is a carbonyl group, O, S, SO₂, or NR¹ where:        -   R¹ is a substituent on a heteroatom which can be the same or            different at each occurrence and is selected from alkyl,            aryl, heteroalkyl and heteroaryl;    -   W is H, alkyl or heteroalkyl; or both of W together can        represent one single bond;    -   in Formula VI:    -   the two E's are in the 1,4-, 1,5-, 1,8-, 2,3-, or 2,6-positions;    -   in Formula VII:    -   the two E's are in the 1,4-, 1,5-, 1,8-, 2,3-, 2,6-, or        9,10-positions;    -   in Formula VIII:    -   a first E is in the 1, 2, or 3 position, a second E is in the 6,        7, or 8 position;    -   in Formula IX:    -   a first E is in the 2; 3, or 4 position; a second E is in the 7,        8, or 9 position; and    -   in Formula XII:    -   R² is selected from hydrogen, alkyl, aryl, heteroalkyl and        heteroaryl;    -   δ is 0 or an integer from 1 to 12.

The invention is further directed to an organic electronic device havingat least one electroactive layer comprising the above copolymer.

As used herein, the term “alkyl” is intended to mean a group derivedfrom an aliphatic hydrocarbon, and includes, linear, branched and cyclicgroups, which may be unsubstituted or substituted. The term“heteroalkyl” is intended to mean a group derived from an aliphatichydrocarbon having at least one heteroatom in the main chain, whichgroup may be unsubstituted or substituted. The term “aryl” is intendedto mean a group derived from an aromatic hydrocarbon, which may beunsubstituted or substituted. The term “heteroaryl” is intended to meana group derived from an aromatic group containing at least oneheteroatom, which group may be unsubstituted or substituted. The term“arylene” is intended to mean a group derived from an aromatichydrocarbon having two points of attachment, which group may beunsubstituted or substituted. The term “heteroarylene” is intended tomean a group derived from an aromatic group having at least oneheteroatom and having two points of attachment, which group may beunsubstituted or substituted. The phrase “adjacent to,” when used torefer to layers in a device, does not necessarily mean that one layer isimmediately next to another layer. On the other hand, the phrase“adjacent R groups,” is used to refer to R groups that are next to eachother in a chemical formula (i.e., R groups that are on atoms joined bya bond). The term “photoactive” refers to any material that exhibitselectroluminescence and/or photosensitivity. The term “electroactive”refers to any material that exhibits hole transport/injection property,electron transport/injection property, electroluminescense, and/orphotosensitivity. The term “monomeric unit” refers to a repeating unitin a polymer. In addition, the IUPAC numbering system is usedthroughout, where the groups from the Periodic Table are numbered fromleft to right as 1–18 (CRC Handbook of Chemistry and Physics, 81^(st)Edition, 2000).

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Formula I and Formula I(a) for the first monomeric unituseful in the invention.

FIG. 2 shows Formula II for the second monomeric unit useful in theinvention.

FIG. 3 shows Formulae II(a) through II(j) for a second monomeric unituseful in the invention.

FIG. 4 shows Formulae II(k) through II(s) for a second monomeric unituseful in the invention.

FIG. 5 shows Formulae II(t) through II(z) for a second monomeric unituseful in the invention.

FIG. 6 shows Formula III and Formulae III(a) through III(g) for a secondmonomeric unit useful in the invention.

FIG. 7 shows Formula IV and Formulae IV(a) through IV(h) for a secondmonomeric unit useful in the invention.

FIG. 8 shows Formula V and Formulae V(a) through V(e) for a secondmonomeric unit useful in the invention.

FIG. 9 shows Formulae VI and Formulae VI(a) through VI(d) for a secondmonomeric unit useful in the invention.

FIG. 10 shows Formula VII and Formula VII(a) for a second monomeric unituseful in the invention.

FIG. 11 shows Formulae VIII through XI for a second monomeric unituseful in the invention.

FIG. 12 shows Formula XII for a substitutent for a second monomeric unituseful in the invention.

FIG. 13 is a schematic diagram of an electronic device that canincorporate the copolymer of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The copolymers of the invention contain at least one of the firstmonomeric units and at least one of the second monomeric units describedabove.

In a first preferred embodiment, the copolymer does not include avinylene monomeric unit. In a second preferred embodiment, the copolymerconsists of optional suitable end-capping groups and at least one firstmonomeric units having Formula I and at least one second monomeric unitselected from Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, and Formula XI.

In a third preferred embodiment, each R group in each of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, and Formula XI is selected from:

hydrogen;

alkyl;

aryl;

heteroalkyl;

heteroaryl;

F;

—CN;

—P(R¹)₂, —SOR¹, where R¹ is a substituent on a heteroatom which can bethe same or different at each occurrence and is selected from alkyl,aryl, heteroalkyl and heteroaryl;

—NO₂;

a beta-dicarbonyl having Formula XII shown in FIG. 12 and as furtherdescribed above;

—C_(ψ)H_(θ)F_(λ);

—OC_(ψ)H_(θ)F_(λ);

—OR¹, —CO₂R¹, —SR¹, —N(R¹)₂, and —SO₂R¹ where R¹ is a straight chain orbranched alkyl of between 1 and 20 carbons or a straight chain orbranched heteroalkyl; or

adjacent R groups together can form a 5- or 6-membered ring selectedfrom cycloalkyl rings, aryl rings and heteroaryl rings. In an embodimentwhere adjacent R groups together form a 5- or 6-membered rings selectedfrom aryl rings and heteroaryl rings, the aryl rings and heteroarylrings are preferably unsubstituted.

First Monomeric Unit

The first monomeric unit is a fluorene-based unit having a Formula Ishown in FIG. 1. The preferred R groups are alkyl groups having 1 to 30carbon atoms, heteroalkyl groups having 1–30 carbon atoms and one ormore heteroatoms of S, N, or O, aryl groups having from 6 to 20 carbonatoms, and heteroaryl groups having from 2 to 20 carbon atoms and one ormore heteroatoms of S, N, or O. Examples of suitable R groups include n-and iso-butyl, pentyls, both linear and branched, hexyls, octyls,including 2-ethylhexyl, up through hexadecyls and above, with andwithout olefinic unsaturation; phenyl, thiophene, carbazole, alkoxy,phenoxy and cyano groups. More preferred R groups on the carbon atom inthe 9-position of the fluorene monomeric unit are linear and branched C₆through C₁₂ alkyls. More preferred R groups on the phenyl rings of thefluorene monomeric unit are H, C₆–C₁₂ alkoxy, phenoxy, C₆–C₁₂ alkyl,phenylorcyano.

An example of a suitable first monomeric unit is shown in FIG. 1 asFormula I(a).

Second Monomeric Unit

The second monomeric unit can be selected from Formulae II through XI asdescribed below.

Formula II:

The second monomeric unit can be an aromatic group having the structureshown in FIG. 2, Formula II. The R groups are preferably selected fromhydrogen;

alkyl;

aryl;

heteroalkyl;

heteroaryl;

F;

—CN;

—NO₂;

a beta-dicarbonyl having Formula XII shown in FIG. 12 and as furtherdescribed above;

—C_(ψ)H_(θ)F_(λ;)

—OC_(ψ)H_(θ)F_(λ); and

—P(R¹)₂, —SOR¹, —OR¹, —CO₂R¹, —SR¹, —N(R¹)₂, and —SO₂R¹ where R¹ is astraight chain or branched alkyl of from 1 to 20 carbons or a straightchain or branched heteroalkyl; or

adjacent R groups together can form a 5- or 6-membered ring selectedfrom cycloalkyl rings, aryl rings and heteroaryl rings.

Alternatively, R groups in Formula II are selected from:

partially or fully fluorinated alkyl groups having from 1 to 12 carbonatoms, especially CF₃;

alkoxy groups having from 1 to 12 carbon atoms; esters having from 3 to15 carbon atoms;

—SR¹, —N(R¹)₂, —P(R¹)₂, —SOR¹, —SO₂R¹, where R¹ is an alkyl group havingfrom 1 to 12 carbon atoms;

—NO₂; and

beta-dicarbonyls having Formula XII shown in FIG. 12, where:

in Formula XII:

R is an alkyl group having from 1 to 12 carbon atoms and δ is 0, 1, or2.

Examples of suitable second monomeric units with Formula II are shown inFIGS. 3 through 5 as Formulae II(a) through II(z) where:

in Formulae II(v) through II(y):

R is as described above for each of Formulae I, II, III, IV, V, VI, VII,VIII through XI.

Formula III:

Alternatively, the second monomeric unit can be a divalent6-membered-ring heteroaromatic group having the structure shown in FIG.6, Formula III. Preferred R groups are hydrogen, C₆–C₁₂alkyl groups,C₆–C₂₀ aryl groups, and C₂–C₂₀ heteroaryl groups. Examples of suitable Elinking groups include pyridinediyl (—C₅H₄N—) and bipyridinediyl(—C₅H₄N—C₅H₄N—).

Examples of suitable second monomeric units having Formula III are shownin FIG. 6 as Formulae III(a) through III(g).

Formula IV:

Alternatively, the second monomeric unit can be a 5-membered-ringheteroaromatic group having the structure shown in FIG. 7, Formula IV.Preferred R groups are hydrogen, C₁–C₁₂ alkyl groups (alternatively,C₁–C₅ alkyl groups or C₆–C₁₂ alkyl groups), C₆–C₂₀ aryl groups, andC₂–C₂₀ heteroaryl groups, more preferably C₆–C₁₂ aryl groups. Examplesof suitable E linking groups include pyrrolediyl (—C₄H₃N—) andthiophenediyl (—C₄H₃S—).

Examples of suitable second monomeric units with Formula IV are shown inFIG. 7 as Formulae IV(a) through IV(h), where:

-   -   in Formula IV(a):    -   R is as described above for each of Formulae I, II, III, IV, V,        VI, VII, VIII through XI; and    -   in Formula IV(h):    -   R¹ is a substituent on a heteroatom which can be the same or        different at each occurrence and is selected from alkyl, aryl,        heteroalkyl and heteroaryl.        Formula V:

Alternatively the second monomeric unit can be an aromatic having thestructure shown in FIG. 8, Formula V. The R groups are preferablyhydrogen, C₁–C₁₂ alkyl groups (alternatively, C₁–C₄ alkyl groups orC₆–C₁₂ alkyl groups), C₆–C₂₀ aryl groups, and C₂–C₂₀ heteroaryl groups.Preferably the two W represent one single bond.

Examples of suitable second monomeric units of this type are thosehaving the structure of Formulae V(a) through Formula V(e) where:

-   -   in Formulae V(a), V(b):    -   R is as described above for each of Formulae I, II, III, IV, V,        VI, VII, VIII through XI; and    -   in Formula V(e):    -   R¹ is a substituent on a heteroatom which can be the same or        different at each occurrence and is selected from alkyl, aryl,        heteroalkyl and heteroaryl.        Formulae VI through XI:

Alternatively the second monomeric unit can be a divalent fused ringaromatic group having the structure shown in FIG. 9, Formula VI, FIG.10, Formula VII, and FIG. 11, Formulae VIII through XI. The R groups arepreferably hydrogen, C₆–C₁₂ alkyl groups, C₆–C₂₀ aryl groups, and C₂–C₂₀heteroaryl groups.

In Formula VI, the E's are preferably in the 1,4-, 1,5-, 1,8-, 2,3-, or2,6-positions. Examples of suitable second monomeric units havingFormula VI are shown in FIG. 9, Formulae VI(a) through VI(d).

In Formula VII, the E's are preferably in the 1,4-, 1,5-, 1,8-, 2,3-,2,6-, or 9,10-positions. An example of a suitable second monomeric unithaving Formula VII is shown in FIG. 10, Formula VII(a).

In the copolymers of the invention, the R groups are essentially sidechains off the polymeric backbone. Thus, the final selection of the Rgroups should take into account the role these side chains may play inthe properties of the final polymer. These properties include electronicproperties, solubility properties, processibility properties,film-forming properties, to enhance or to reduce interchain interaction,to induce solubility in organic solvents, to induce compatibility inblends with host polymers, to induce high dielectric constant so as tosolvate ions, to enhance ionic mobility, etc. In addition, where the Rgroups are substituted, steric effects of such substituents should beconsidered in substituent selection.

In the copolymer of the invention, more than one of the second monomericunits can be present with the first monomeric unit. The relative molarproportion of first monomeric unit to the at least one second monomericunit(s) can be from 99.9:0.1 to 1:99 or 99.5:0.5 to 10:90; alternatively99:1 to 20:80, and further alternatively 99:1 to 50:50. Theincorporation of the monomers in the formation of the polymer can berandom or controlled, resulting in copolymers which include, but are notlimited to, random copolymers, alternating copolymers and blockcopolymers.

Synthesis

The copolymers of the invention can generally be prepared by three knownsynthetic routes. In the first synthetic method, as described inYamamoto, Progress in Polymer Science, Vol. 17, p 1153 (1992), thedihalo derivatives of the monomeric units are reacted with astoichiometric amount of a zerovalent nickel compound, such asbis(1,5-cyclooctadiene)nickel(0). In the second method, as described inColon et al., Journal of Polymer Science, Part A, Polymer chemistryEdition, Vol. 28, p. 367 (1990). The dihalo derivatives of the monomericunits are reacted with catalytic amounts of Ni(II) compounds in thepresence of stoichiometric amounts of a material capable of reducing thedivalent nickel ion to zerovalent nickel. Suitable materials includezinc, magnesium, calcium and lithium. In the third synthetic method, asdescribed in U.S. Pat. No. 5,962,631, and published PCT application WO00/53565, a dihalo derivative of one monomeric unit is reacted with aderivative of another monomeric unit having two reactive groups selectedfrom boronic acid, boronic acid esters, and boranes, in the presence ofa zerovalent palladium catalyst, such as tetrakis(triphenylphosphine)Pd.

In some embodiments of the invention, the copolymer can be reacted withan end-capping compound to convert the reactive end group to anon-reactive end group. The end-capping compound is generally added to apreformed polymer and ends the polymerization reaction. The end-cappingcompound is generally an aromatic compound having a single reactivegroup, such as an aromatic ring having a single halide group or boronicacid or ester group. Examples of suitable end-capping compounds include9-bromoanthracene, 4-bromo-1,2-dimethoxybenzene, 1-bromopyrene,iodobenzene, bromobenzene, 2-bromo-9-fluorenone, and benzeneboronicacid. The end-capping group may also be designed to add functionality,such as charge transport properties and color shifting. It may alsoaffect interchain aggregation.

Electronic Device

The present invention also relates to an electronic device comprising atleast one photoactive layer positioned between two electrical contactlayers, wherein at least one of the electroactive layers of the deviceincludes the copolymer of the invention. As shown in FIG. 13, a typicaldevice 100 has an anode layer 110 and a cathode layer 150 andelectroactive layers 120,130 and optionally 140 between the anode 110and cathode 150. Adjacent to the anode is a hole injection/transportlayer 120. Adjacent to the cathode is an optional layer 140 comprisingan electron injection/transport material. Between the holeinjection/transport layer 120 and the cathode (or optional electrontransport layer) is the photoactive layer 130. The copolymers of theinvention can be useful in the hole injection/transport layer 120 and/orin the photoactive layer 130 and/or the optional electroninjection/transport layer 140.

The device generally also includes a support (not shown) which can beadjacent to the anode or the cathode. Most frequently, the support isadjacent the anode. The support can be flexible or rigid, organic orinorganic. Generally, glass or flexible organic films are used as asupport. The anode 110 is an electrode that is particularly efficientfor injecting or collecting positive charge carriers. The anode ispreferably made of materials containing a metal, mixed metal, alloy,metal oxide or mixed-metal oxide. Suitable metals include the Group 11metals, the metals in Groups 4, 5, and 6, and the Group 8–10 transitionmetals. If the anode is to be light-transmitting, mixed-metal oxides ofGroups 12, 13 and 14 metals, such as indium-tin-oxide, are generallyused. The anode 110 may also comprise an organic material such aspolyaniline as described in “Flexible light-emitting diodes made fromsoluble conducting polymer,” Nature vol. 357, pp 477–479 (11 Jun. 1992).

The anode layer is 110 usually applied by a physical vapor depositionprocess or spin-cast process. The term “physical vapor deposition”refers to various deposition approaches carried out in vacuo. Thus, forexample, physical vapor deposition includes all forms of sputtering,including ion beam sputtering, as well as all forms of vapor depositionsuch as e-beam evaporation and resistance evaporation. A specific formof physical vapor deposition which is useful is rf magnetron sputtering.

The copolymers of the invention may function as hole transport materialsin layer 120. Other materials which may facilitate holeinjection/transport includeN,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD) andbis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),and hole transport polymers such as polyvinylcarbazole (PVK),(phenylmethyl)polysilane, poly(3,4-ethylenedioxythiophene) (PEDOT), andpolyaniline (PANI);electron and hole transporting materials such as4,4′-N,N′-dicarbazole biphenyl (BCP); or light-emitting materials withgood electron and hole transport properties, such as chelated oxinoidcompounds, such as tris(8-hydroxyquinolato)aluminum (Alq₃).

The hole injection/transport layer 120 can be applied using anyconventional means, including spin-coating, casting, and printing, suchas gravure printing. The layer can also be applied by ink jet printing,thermal patterning, or physical vapor deposition.

In general, the anode 110 and the hole injection/transport layer 120 ispatterned. It is understood that the pattern may vary as desired. Thelayers can be applied in a pattern by, for example, positioning apatterned mask or photoresist on the first flexible composite barrierstructure prior to applying the first electrical contact layer material.Alternatively, the layers can be applied as an overall layer andsubsequently patterned using, for example, a photoresist and wetchemical etching. The hole injection/transport layer can also be appliedin a pattern by ink jet printing, lithography or thermal transferpatterning. Other processes for patterning that are well known in theart can also be used.

Depending upon the application of the device 100, the photoactive layer130 can be a light-emitting layer that is activated by an appliedvoltage (such as in a light-emitting diode or light-emittingelectrochemical cell), a layer of material that responds to radiantenergy and generates a signal with or without an applied bias voltage(such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are describe inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

Where the device 100 is a light-emitting device, the photoactive layer130 will emit light when sufficient bias voltage is applied to theelectrical contact layers. The copolymers of the invention may be usedin the light-emitting active layer 130. Other known light-emittingmaterials include small molecule materials such as those described in,for example, Tang, U.S. Pat. No. 4,356,429, Van Slyke et al., U.S. Pat.No. 4,539,507, the relevant portions of which are incorporated herein byreference. Alternatively, such materials can be polymeric materials suchas those described in Friend et al. (U.S. Pat. No. 5,247,190), Heeger etal. (U.S. Pat. No. 5,408,109), Nakano et al. (U.S. Pat. No. 5,317,169),the relevant portions of which are incorporated herein by reference. Thelight-emitting materials may be dispersed in a matrix of anothermaterial, with and without additives, but preferably form a layer alone.The active organic layer generally has a thickness in the range of50–500 nm.

Where the electronic device 100 is a photodetector, the photoactivelayer 130 responds to radiant energy and produces a signal either withor without a biased voltage. Materials that respond to radiant energyand is capable of generating a signal with a biased voltage (such as inthe case of a photoconductive cells, photoresistors, photoswitches,phototransistors, phototubes) include, for example, many conjugatedpolymers and electroluminescent materials. Materials that respond toradiant energy and are capable of generating a signal without a biasedvoltage (such as in the case of a photoconductive cell or a photovoltaiccell) include materials that chemically react to light and therebygenerate a signal. Such light-sensitive chemically reactive materialsinclude for example, many conjugated polymers and electro- andphoto-luminescent materials. Specific examples include, but are notlimited to, MEH-PPV (“Optocoupler made from semiconducting polymers”, G.Yu, K. Pakbaz, and A. J. Heeger, Journal of Electronic Materials, Vol.23, pp 925–928 (1994); and MEH-PPV Composites with CN-PPV (“EfficientPhotodiodes from Interpenetrating Polymer Networks”, J. J. M. Halls etal. (Cambridge group) Nature Vol. 376, pp. 498–500, 1995).

The photoactive layer 130 containing the active organic material can beapplied from solutions by any conventional means, includingspin-coating, casting, and printing. The active organic materials can beapplied directly by vapor deposition processes, depending upon thenature of the materials. It is also possible to apply an active polymerprecursor and then convert to the polymer, typically by heating.

The cathode 150 is an electrode that is particularly efficient forinjecting or collecting electrons or negative charge carriers. Thecathode can be any metal or nonmetal having a lower work function thanthe first electrical contact layer (in this case, an anode). Materialsfor the second electrical contact layer can be selected from alkalilmetals of Group 1 (e.g., Li, Cs), the Group 2 (alkaline earth) metals,the Group 12 metals, the rare earths, the lanthanides, and theactinides. Materials such as aluminum, indium, calcium, barium, andmagnesium, as well as combinations, can be used.

The cathode layer 150 is usually applied by a physical vapor depositionprocess. In general, the cathode layer will be patterned, as discussedabove in reference to the anode layer 110 and conductive polymer layer120. Similar processing techniques can be used to pattern the cathodelayer.

Optional layer 140 can function both to facilitate electron transport,and also serve as a buffer layer or confinement layer to preventquenching reactions at layer interfaces. Preferably, this layer promoteselectron mobility and reduces quenching reactions. Examples of electrontransport materials for optional layer 140 include metal chelatedoxinoid compounds, such as tris(8-hydroxyquinolato)aluminum (Alq₃);phenanthroline-based compounds, such as2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA) or4,7-diphenyl-1,10-phenanthroline (DPA), and azole compounds such as2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ).

It is known to have other layers in organic electronic devices. Forexample, there can be a layer (not shown) between the conductive polymerlayer 120 and the active layer 130 to facilitate positive chargetransport and/or band-gap matching of the layers, or to function as aprotective layer. Similarly, there can be additional layers (not shown)between the active layer 130 and the cathode layer 150 to facilitatenegative charge transport and/or band-gap matching between the layers,or to function as a protective layer. Layers that are known in the artcan be used. In addition, any of the above-described layers can be madeof two or more layers. Alternatively, some or all of inorganic anodelayer 110, the conductive polymer layer 120, the active layer 130, andcathode layer 150, may be surface treated to increase charge carriertransport efficiency. The choice of materials for each of the componentlayers is preferably determined by balancing the goals of providing adevice with high device efficiency.

The device 100 can be prepared by-sequentially depositing the individuallayers on a suitable substrate. Substrates such as glass and polymericfilms can be used. In most cases the anode is applied to the substrateand the layers are built up from there. However, it is possible to firstapply the cathode to a substrate and add the layers in the reverseorder. In general, the different layers will have the following range ofthicknesses: inorganic anode 110, 500–5000 Å, preferably 1000–2000 Å;conductive polymer layer 120, 50–2500 Å, preferably 200–2000 Å;light-emitting layer 130, 10–1000 Å, preferably 100–800 Å; optionalelectron transport layer 140, 50–1000 Å, preferably 200–800 Å; cathode150, 200–10000 Å, preferably 300–5000 Å.

EXAMPLES

The following examples illustrate certain features and advantages of thepresent invention. They are intended to be illustrative of theinvention, but not limiting. All percentages are by weight, unlessotherwise indicated.

Examples 1–5 and Examples 1A–5A

Examples 1–5 illustrate the preparation of the copolymers of theinvention using dihalo monomers and zerovalent nickel. The copolymerswere characterized by Nuclear Magnetic Resonance (NMR) and the numberaverage molecular weights (M_(n)) determined by Gel PermeationChromatography (GPC).

Example 1

Under inert conditions, DMF (5 ml) was added to a 50 ml Schlenck tubeequipped with a stirring bar and containingbis(1,5-cyclooctadiene)nickel(0) (1.23 g, 4.48 mmol), 2,2′-bipyridyl(0.70 g, 4.48 mmol), and 1,5-cyclooctadiene (0.48 g, 4.48 mmol). Theensuing deep blue/purple solution was stirred at 60° C. for 30 minutes,and then a solution of a first monomer,2,7-diiodo-9,9-bis(2-ethylhexyl)fluorene (1.08 g, 1.68 mmol) and asecond monomer, 2,5-bis(p-bromophenyl)-N-(p-hexylphenyl)pyrrole (0.30 g,0.56 mmol) in toluene (20 ml) was added via syringe. The reactionmixture was then stirred at 75° C. for 5 days. The mixture was cooled toroom temperature and precipitated into a solution of methanol (100 ml),acetone (100 ml) and concentrated hydrochloric acid (5 ml). Afterstirring for 2 hours, the mixture was filtered. The solid residue wasthen dissolved in chloroform, and again precipitated into a solution ofmethanol (100 ml), acetone (100 ml) and concentrated hydrochloric acid(5 ml). After stirring for 1 hour, the mixture was filtered. Finally theresidue was successively washed with methanol, water and methanol anddried in vacuo. The molecular weight is given in Table 1 below.

Example 1A

The procedure of Example 1 was repeated, except that the reactionmixture was stirred at 75° C. for 24 hours, instead of for 5 days. Inaddition, after the mixture was filtered, the resulting solid was againdissolved in chloroform and precipitated in pure methanol, before theresidue was sucessively washed with methanol, water and methanol anddried in vacuo. Essentially the same molecular weight provided in Table1 below were obtained.

Examples 2–5

The procedure of Example 1 was repeated using2,7-dibromo-9,9-bis(2-ethylhexyl)fluorene as the first monomer anddifferent second monomers, and with the addition of iodobenzene as anendcapping group. The reaction mixture without endcapper was heated withstirring for 4 days, the iodobenzene endcapper was added, and themixture was stirred at 75° C. for another day. The copolymers aresummarized in Table 1 below.

Examples 2A–5A

The procedure of Examples 2–5 was repeated, except that bromobenzene wasadded instead of iodobenzene as an endcapping group. The reactionmixutre was heated with stirring for 24 hours instead of 4 days beforethe bromozene endcapper was added, and the mixture was stirred foranother hour, instead of another day. The copolymers obtained weresimilar to those summarized in Table 1 below.

TABLE 1 Fluorene Copolymers Ratio* 1^(st) 1^(st) to 2^(nd) to Ex.monomer 2^(nd) monomer endcap M_(n) 1 diiodo2,5-bis(p-bromophenyl)-N-(p- 3:1:0 47,200 hexylphenyl)pyrrole 2 dibromomethyl-3,5-dibromobenzoate 10:1:1.1 68,700 3 dibromomethyl-2,5-dibromobenzoate 10:1:1.1 98,400 4 dibromo2,5-bis(4-bromophenyl) 10:1:1.1 67,300 oxadiazole 5 dibromo2,7-dibromo-9-fluorenone 10:1:1.1 60,900 *Ratio is the molar ratio ofthe starting materials

Examples 6 and 6A

This example illustrates the preparation of fluorene copolymers using adihalo monomer, a diboronic acid ester monomer and a palladium catalyst.

Example 6

Under an argon atmosphere, toluene (10 ml) was added to a 50 ml Schlencktube equipped with a stirring bar and containing2,7-diiodo-9,9-bis(2-ethylhexyl) fluorene (1.07 g, 1.66 mmol) and1,4-benzenediboronicacid bis(neopentyl glycol) cylic ester (0.50 g, 1.66mmol). Then tetrakis(triphenylphosphine)palladium (0) (19 mg, 0.0166mmol) and a degassed aqueous potassium carbonate solution (2M, 7.0 ml)were added to the tube. The solution was heated in an oil bath at 100°C. for 48 hours with vigorous stirring. The end-capper,4-methylbenzeneboronic acid (50 mg, 0.33 mmol), was added and themixture heated with stirring for an additional 12 hours. The mixture wascooled to room temperature, and then precipitated into a solution ofmethanol (100 ml), acetone (100 ml) and concentrated hydrochloric acid(5 ml). After stirring for 2 hours, the mixture was filtered. The solidresidue was then dissolved in chloroform, and again precipitated into asolution of methanol (100 ml), acetone (100 ml) and concentratedhydrochloric acid (5 ml). After stirring for 1 hour, the mixture wasfiltered. Finally the residue was successively washed in methanol, waterand methanol and dried in vacuo. The resulting copolymer had a molecularweight (M_(n)) of 8800.

Example 6A

Under an argon atmosphere, toluene (10 ml) was added to a 50 ml Schlencktube equipped with a stirring bar and containing2,7-diiodo-9,9-bis(2-ethylhexyl) fluorene (1.07 g, 1.66 mmol) and1,4-benzenediboronicacid bis(neopentyl glycol) cylic ester (0.50 g, 1.66mmol). Then tetrakis(triphenylphosphine)palladium (0) (19 mg, 0.0166mmol) and a degassed aqueous potassium carbonate solution (2M, 7.0 ml)were added to the tube. The solution was heated in an oil bath at 100°C. for 48 hours with vigorous stirring. The first end-capper,benzeneboronic acid (50 mg, 0.33 mmol), was added and the mixture heatedwith stirring for an additional 1 hour. The second end-capper,bromobenzene (50 mg), was added and the mixture was heated and stirredfor an additional hour. The mixture was then cooled to room temperature,and then precipitated into a solution of methanol. The mixture wasfiltered and the residue was washed with methanol and dried in vacuum.The resulting copolymer had a molecular weight (M_(n)) of 8800.

Example 7–17

The copolymers of Examples 1–5 above were tested as light-emitters in alight emitting diode having the layers illustrated in FIG. 13, with themodification of a substrate supporting the anode. The anode used wasindium tin oxide (ITO), supported by a glass substrate. The holeinjection/transport layer was spin-coated onto the ITO on glasssubstrate. The hole injection/transport layer waspoly(3,4-ethylenedioxythiophene), PEDOT, (Baytron® P from Bayer,Germany) at a thickness of about 2000 Å or a bilayer of PEDOT andpolyvinylcarbazole, PVK, at a total thickness of about 2000 Å. Thecopolymer was dissolved in toluene to form a 2.0% (w/v) solution,filtered through a 0.22 micron filter, and spin-coated over the holeinjection/transport layer. The target thickness of the copolymer layerwas 800 Å, with actual thicknesses typically in the range of 500 to 1000Å.

For the cathode, Ba and Al layers were sequentially vapor deposited ontop of the EL layers under a vacuum of 1×10⁻⁶ torr. The final thicknessof the Ba layer was 30 Å; the thickness of the Al layer was 3000 Å.Device performance was tested inside a dry box using a calibrated Siphotodiode. The results are given in Table 2 below.

TABLE 2 Hole Cd/A EL Injection/ Voltage at Cd/A Cd/m² QE % ExamplePolymer Transport at 100 Cd/m² 25 mA (at mA) (at V) (at V) 7 Ex. 1 PEDOT849 0.18 (12 V) (12 V) 8 Ex. 1 PEDOT/PVK 669 0.11 (14 V) (14 V) 9 Ex. 1PVK 3970  0.62 (14 V) (14 V) 10 Ex. 2 PEDOT/PVK 8.6 0.76 0.86 (34 mA) 11Ex. 2 PVK 6.6 0.06  0.068 (55 mA) 12 Ex. 3 PEDOT/PVK 9.1 1.19 1.22 (35mA) 13 Ex. 3 PVK 6.9 0.2 0.22 (20 mA) 14 Ex. 4 PEDOT/PVK >10 0.68 0.87(3 mA) 15 Ex. 4 PVK 9.1 0.46 0.50 (50 mA) 16 Ex. 5 PEDOT/PVK >10 1.143.74 (0.04 mA) 17 Ex. 5 PVK >10 1.2 1.5  (8 mA) 

While this invention has been described with respect to what is atpresent considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent formulations and functions.

1. A copolymer consisting essentially of at least one first monomericunit and at least one second monomeric unit, wherein the at least onefirst monomeric unit has a Formulae I and I(a)

and the at least one second monomeric unit is selected from5-membered-ring heteroaromatic groups having Formula IV

in each of Formulae I and IV: R is a substituent on a carbon atom whichcan be the same or different at each occurrence and is selected fromhydrogen, alkyl, aryl, heteroalkyl, heteroaryl, F, —CN, —OR¹, —CO₂R¹,—C_(ψ)H_(θ)F_(λ), —OC_(ψ)H_(θ)F_(λ), —SR¹, —N(R¹)₂, —P(R¹)₂, —SOR¹,—SO₂R¹, —NO₂, and beta-dicarbonyls having Formula XII

 or adjacent R groups together can form a 5- or 6-membered cycloalkyl,aryl, or heteroaryl ring, such that: R¹ is a substituent on a heteroatomwhich can be the same or different at each occurrence and is selectedfrom alkyl, aryl, heteroalkyl and heteroaryl; and ψ is an integerbetween 1 and 20, and θ and λ are integers satisfying Equation A1 below:θ+λ=_(ψ)+1;  (Equation A1); in Formula IV: E can be the same ordifferent at each occurrence and is a single bond or a linking groupselected from arylene and heteroarylene; in Formula IV: A isindependently at each occurrence C or N and γ is 0 or an integerselected from 1 or 2, such that when both A are N, then γ is 0; or whenone of A is N and one of A is C, then γ is 1; or when both A are C, thenγ is 2; Q is O, S, SO₂, or NR¹ where: R¹ is a substituent on aheteroatom which can be the same or different at each occurrence and isselected from alkyl, aryl, heteroalkyl and heteroaryl; in Formula XII:R² is selected from hydrogen, alkyl, aryl, heteroalkyl and heteroaryl; δis 0 or an integer from 1 to 12, and when R in formula IV is hydrogen,alkyl, F, —CN, —OR¹, or CO₂R¹ the copolymer further comprisesend-capping groups that are aromatic.
 2. The copolymer of claim 1,wherein R groups in one or more of the at least one first monomeric unitare independently selected from alkyl groups having 1 to 30 carbonatoms; heteroalkyl groups having 1–30 carbon atoms and one or moreheteroatoms of S, N, or O; aryl groups having from 6 to 20 carbon atoms,and heteroaryl groups having from 2 to 20 carbon atoms and one or moreheteroatoms of S, N, or O.
 3. The copolymer of claim 1 that excludes anyvinylene monomeric units.
 4. The copolymer of claim 1 wherein each Rgroup in each of Formula I, Formula I(a), and Formula IV is selectedfrom: hydrogen; alkyl; heteroalkyl; heteroaryl; F; —CN; —P(R¹)₂ and—SOR¹, where R¹ is a substituent on a heteroatom which can be the sameor different at each occurrence and is selected from alkyl, aryl,heteroalkyl and heteroaryl; —NO₂; a beta-dicarbonyl having Formula XII

—C_(ψ)H_(θ)F_(λ); —OC_(ψ)H_(θ)F_(λ); —OR¹, —CO₂R¹, —SR¹, —N(R¹)₂, and—SO₂R¹ where R¹ is a straight chain or branched alkyl of more than 20carbons or a straight chain or branched heteroalkyl.
 5. The copolymer ofclaim 1 wherein the at least one of the R groups in one or more of theat least one first monomeric unit is independently selected from linearand branched n-butyl groups; linear and branched iso-butyl groups;linear and branched pentyl groups; hexyl groups, and octyl groups withand without olefinic unsaturation; phenyl groups, thiophene groups,carbazole groups, alkoxy groups, phenoxy groups and cyano groups.
 6. Thecopolymer of claim 1 wherein at least one of the R groups in one or moreof the at least one first monomeric unit are independently selected fromH, C₆–C₁₂ alkoxy, phenoxy, C₆–C₁₂ alkyl, phenyl and cyano.
 7. Thecopolymer of claim 1 wherein one or more of the at least one secondmonomeric unit is selected from Formulae I, I(a), and IV(a) throughIV(h):

where: in Formula IV(a): R is as described above for each of Formulae I,I(a) and IV; in Formula IV(h): R¹ is a substituent on a heteroatom whichcan be the same or different at each occurrence and is selected fromalkyl, aryl, heteroalkyl and heteroaryl.
 8. The copolymer of claim 1,wherein one or more of the at least one second monomeric unit hasFormula IV wherein R is selected from: partially or fully fluorinatedalkyl groups having from 1 to 12 carbon atoms; alkoxy groups having from1 to 12 carbon atoms; esters having from 3 to 15 carbon atoms; —SR¹,—N(R¹)₂, —P(R¹)₂, —SOR¹, —SO₂R¹, where R¹ is an alkyl group having from1 to 12 carbon atoms; —NO_(2;) and beta-dicarbonyls having Formula XIIwhere:

in Formula XII: R² is an alkyl group having from 1 to 12 carbon atomsand δ is 0, 1, or
 2. 9. The copolymer of claim 1, wherein one or more ofthe at least one second monomeric unit has Formula IV wherein: R groupsare selected from H, C₆–C₁₂ alkyl groups, C₆–C₂₀ aryl groups, and C₂–C₂₀heteroaryl groups; and E linking groups include pyrrolediyl (—C₄H₃N—)and thiophenediyl (—C₄H₃S—).
 10. An electronic device comprising atleast one electroactive layer comprising the copolymer of claim
 1. 11.The device of claim 10, wherein the device comprises a holeinjection/transport layer comprising the copolymer of claim
 1. 12. Thedevice of claim 10, wherein the device comprises an electroninjection/transport layer comprising the copolymer of claim
 1. 13. Thedevice of claim 10, wherein the electroactive layer comprises alight-emitting material comprising the copolymer of claim
 1. 14. Thedevice of claim 10, wherein the device is selected from a light-emittingdevice, a photodetector, and a photovoltaic device.
 15. The device ofclaim 10, wherein the device is an electroluminescent display.
 16. Alight-emitting device comprising at least one light-emitting layercomprising the following consisting essentially of at least one firstmonomeric unit and at least one second monomeric unit, wherein the atleast one first monomeric unit has a Formulae I and I(a).

and the at least one second monomeric unit is selected from5-membered-ring heteroaromatic groups having Formula IV

in each of Formulae I and IV: R is a substituent on a carbon atom whichcan be the same or different at each occurrence and is selected fromhydrogen, alkyl, aryl, heteroalkyl, heteroaryl, F, —CN, —OR¹, —CO₂R¹,—C_(ψ)H_(θ)F_(λ), —OC_(ψ)H_(θ)F_(λ), —SR¹, —N(R¹)₂, —P(R¹)₂, —SOR¹,—SO₂R¹, —NO₂, and beta-dicarbonyls having Formula XII

 or adjacent R groups together can form a 5- or 6-membered cycloalkyl,aryl, or heteroaryl ring, such that: R¹ is a substituent on a heteroatomwhich can be the same or different at each occurrence and is selectedfrom alkyl, aryl, heteroalkyl and heteroaryl; and ψ is an integerbetween 1 and 20, and θ and λ are integers satisfying Equation A1 below:θ+λ=2_(ψ)1;  (Equation A1); in Formula IV: E can be the same ordifferent at each occurrence and is a single bond or a linking groupselected from arylene and heteroarylene; in Formula IV: A isindependently at each occurrence C or N and γ is 0 or an integerselected from 1 or 2, such that when both A are N, then γ is 0; or whenone of A is N and one of A is C, then γ is 1; or when both A are C, thenγ is 2; Q is O, S, SO₂, or NR¹ where: R¹ is a substituent on aheteroatom which can be the same or different at each occurrence and isselected from alkyl, aryl, heteroalkyl and heteroaryl; in Formula XII:R²is selected from hydrogen, alkyl, aryl, heteroalkyl and heteroaryl; δis 0 or an integer from 1 to 12.